Scent plays an important role in human behavior. Scents can evoke powerful emotions. One need only recall the flood of emotions reported by Marcel Proust in “Remembrance of Things Past” when he dipped his madeleine into his tea and their unique blend of odors were released. This may be due to the close anatomical ties between the olfactory system and the limbic system and hippocampus, areas of the brain that have long been known to be involved in emotion and place memory, respectively. See Nieuwenhuys, The Greater Limbic System, the Emotional Motor System, and the Brain, 107 Prog. Brain Res. 551 (1996). Some commentators have suggested that 75% of emotions are generated by smell. See, e.g., Bell & Bell, Future Sense: Defining Brands Through Scent, 38 J. Market. Soc. 38 (2007).
By virtue of its effect on emotions, scent can play a role in a variety of common behaviors. By way of example, scent is implicated in mate selection. Men exposed to the scent of an ovulating woman subsequently displayed higher levels of testosterone than did men exposed to the scent of a non-ovulating woman or a control scent, suggesting that olfactory cues signaling women's levels of reproductive fertility are associated with specific endocrinological responses in men that are linked to the initiation of romantic courtship. See Miller, Scent of a Woman: Men's Testosterone Responses to Olfactory Ovulation Cues, 21 Psychological Science 276-83 (2010). Scent may also play a role in therapeutic medical treatment. In women, the sense of olfaction is strongest around the time of ovulation, significantly stronger than during other phases of the menstrual cycle and also stronger than the sense in males. See Navarrete-Palacios, et al., Lower Olfactory Threshold During the Ovulatory Phase of the Menstrual Cycle, 63 Biolog. Psychol. 269-79 (2003).
The field of aromatherapy posits that essential oils and other aromatic compounds may alter a person's mind, mood, cognitive function, and health. See Edris, Pharmaceutical and Therapeutic Potentials of Essential Oils and Their Individual Volatile Constituents: A Review, 21 Phytotherapy Res. 308-23 (2007).
Scents can also influence consumer shopping habits. In 2006, scent marketing was touted as one of the top ten trends to watch. See Thomaselli, Trends to Watch in 2007, 77 Advertising Age 10 (2006). Many retailers, hotels, and restaurants investing in scent marketing with the belief that carefully selected scents will influence consumer spending, attract customers, and create memorable brands. See Dowdey, Does what you smell determine what you buy?, in How Stuff Works (Dec. 27, 2007), available on Mar. 17, 20012, at <http://money.howstuffworks.com/scent-marketing.htm>. As a result, the scent marketing industry is a $100 million business and is predicted to reach up to $1 billion within the next few years. See Ravn, Smells Like Sales, L.A. Times F-1 (Aug. 20, 2007).
The importance of scent to humans is reflected in the size of the international perfume industry. Current retail sales are between $25 billion and $30 billion worldwide. Burr, Perfumers Breathe in Sales Data, and Strategize, N.Y. Times, Bus. Sec. (Jun. 19, 2009). Sales are expected to exceed $33 billion by 2015. Global Industry Analysts, Inc., Fragrances and Perfumes—A Global Strategic Business Report (2011).
Most scents are derived from organic materials—plants, animals, and other natural sources. Most scents are derived from plants, including plant barks (such as cinnamon, cascarilla, and sassafras), flowers and blossoms (such as rose, jasmine, tuberose, and narcissus), fruits (such as orange, lemon, and lime), leaves and twigs (such as lavender, patchouli, and sage), resins (such as frankincense, myrrh, and pine), roots, rhizomes and bulbs (such as iris, vetiver, and ginger), seeds (such as coriander, cardamom, and anise), and woods (such as sandalwood, cedar, and juniper). Animal scent sources include ambergris (from the sperm whale), castoreum (form the North American beaver), musk (from the civet—a relative of the mongoose—or the Asian musk deer), hyraceum (the petrified excrement of the Rock Hyrax), and honeycomb (from the honeycomb of the honeybee). Other natural sources include lichens (such as oakmoss and treemoss thalli) and seaweed (such as Fucus vesiculosus). Other scents comprise synthesized scents. Synthetics can provide scents not found in nature (such as Calone), as well as scents too expensive to harvest from natural sources (such as linalool, orchid scents, and white musk) and fragrances that, in their natural form, are toxic to humans (such as coumarin, which is a carcinogen).
Various electronic devices have been proposed for the generation of scents. Examples of commercially available devices include the Scent Generator Classic (Biophysical Human Research Institute, Ljubljana, Slovenia), Fragrance Communication (NTT Communications Corporation, Tokyo, Japan), Odoravision (Olf Action, Paris, France), Scent-Dome (TriSenx, Inc., Savannah, Ga., USA), Kaori Web (K-Opticom Corporation, Tokyo, Japan), and the ScentScape Programmable Aroma Generator (Scent Sciences Corporation, San Jose, Calif., USA). Each of these devices store one or more scented substances (which may be organic or synthetic), the innate scents of which are activated with heat. In some cases, two or more substances are activated, and the activated scents combine to form a different scent.
The devices of the prior art are subject to several limitations. One such limitation is that the number of scents a device can generate is limited by the number of scented substances stored in the device. Even taking combinatorial scents into account, the capacity of the device to generate a vast number of scents requires storage of a vast number of substances, which, albeit possible, impedes the potential for broad distribution to consumers.
Another limitations of the prior art is that none of these devices includes a mechanism for suppressing or extinguishing a scent once generated. Instead, the scent continues to be activated until the activating stimulus dissipates. By analogy to musical notes, this limitation is akin to a piano with no damper, wherein each note played would continue to be heard until the vibration of the string ceases. This limitation could be partially overcome by subjecting the scent substances to a stimulus antipodal to the activating mechanism. By way of example, if heat is used to activate a given substance, the scent could be suppressed or “damped” by cooling the substance with a cryogen liquid or gas (such as argon, carbon dioxide, chlorodifluoromethane, chloropentafluoroethane, chlorotrifluoromethane, clean dry air, compressed air, dichlorofluoromethane, dichlorofluoromethane, floroform, helium, hexafluoroethane, krypton, neon, nitrogen, perfluoropentane, sulfur hexafluoride, tetrafluoromethane, trichlorofluoromethane, trichlorofluoromethane, or xenon). This would require, however, that the device include both the material and application mechanism of the antipodal stimulus, thereby adding more size, weight, and complexity to the device. Moreover, these antipodal materials can be harmful to the environment, the health and safety of the user, or both. The health and safety risks of cryogens, for example, include contact burns, frostbite, asphyxiation, toxicity, and hypothermia. In addition, even if the scent activation is suppressed, those scent molecules already released into the atmosphere would continue to linger until they dissipate in due course. The value of electronic scent generation is control over the scents produced. The inability to suppress or extinguish a scent fully at will is a limitation that undermines the benefits of the device.
A third limitations of the prior art is size and weight. In order to store a critical mass of scent substances and the mechanism required to activate the same, these scent generating devices are necessarily large. In addition, their portability is limited by the risks associated with leakage of scent substances and activation stimuli (such as heat).
There is a need for an electronic scent generator that is able to produce a vast array of scents without having to store a large number of scent substances and is further able to extinguish those scents as and when desired. Ideally, the device would be sufficiently compact to occupy desktops and living rooms and would be susceptible to production in both portable and wearable versions.